1. Field of the Invention
The present invention relates to an optical head and an optical head device, and more particularly to an optical head which is suited to be used for high-density recording/reading/erasing of information to or from an optical recording medium and an optical head device using this optical head.
2. Description of Related Art
In the art of optical memories which optically record and read information, in recent years, with speed-up of computer processing and development of multimedia, high-density devices which are capable of recording an extremely large volume of information are demanded, and in order to comply with the demand, a near field optical recording technique is suggested. In a conventional optical memory using a laser beam, the recording density is limited depending on the diffraction limit of light, and such an optical memory can record and read marks of sizes at least light wavelength (several hundred nanometers). A recently proposed optical memory which uses near field optics radiates light to a recording medium (optical disk) for recording/reading with the optical head and the recording medium arranged at an interval of only some dozen nanometers. At this time, the optical memory uses a fiber probe with a minuscule aperture smaller than light wavelength and a solid immersion lens. Thereby, in spite of the diffraction limit, it becomes possible to record and read minuscule marks of some dozen nanometers.
In a conventional memory which uses propagated light, such as a CD, a DVD, an MO or the like, a convergent lens, a mirror, a prism and other optical elements are installed in the optical head, and the optical head is large and heavy. It is, therefore, difficult to adopt an air floating method based on the air lubricating principle, which is generally adopted in magnetic recording heads, in such an optical memory. In the above-mentioned optical head using a solid immersion lens, although the solid immersion lens itself is small and light, it is necessary to further use a convergent lens, which indispensably increases the size and weight.
Lately, “Objective Lenses for DVD& Near Field Optical Disk Pick-up” ODF'98, Tokyo, Jun. 16, 1998 suggests an SIM (solid immersion mirror) which does not require a convergent lens. This SIM converges light by performing refraction once and reflection twice in a prism. Since this eliminates the necessity of using a convergent lens, an optical head using this SIM is small and light. However, because the SIM uses a coaxial optical system, the design is strongly limited. Also, since a direction of light incident to the SIM is perpendicular to a recording surface, a mirror for bending optical path of incident light is required. Accordingly, vibration and shift of the mirror must be adjusted, which obstructs reduction of the size and weight of the optical head device.